Improve shaping segmentation for grapheme cluster based font fallback

third_party/WebKit/Source/platform/fonts/shaping/HarfBuzzShaper.h

Index: third_party/WebKit/Source/platform/fonts/shaping/HarfBuzzShaper.h
diff --git a/third_party/WebKit/Source/platform/fonts/shaping/HarfBuzzShaper.h b/third_party/WebKit/Source/platform/fonts/shaping/HarfBuzzShaper.h
index b851ac2464f7fd0bd5c7f15a3e810e83765f8ece..7f0b994078a1dc7efa96980154f34ef48e7d6ae7 100644
--- a/third_party/WebKit/Source/platform/fonts/shaping/HarfBuzzShaper.h
+++ b/third_party/WebKit/Source/platform/fonts/shaping/HarfBuzzShaper.h
@@ -36,6 +36,7 @@
 #include "platform/geometry/FloatPoint.h"
 #include "platform/geometry/FloatRect.h"
 #include "platform/text/TextRun.h"
+#include "wtf/Deque.h"
 #include "wtf/HashSet.h"
 #include "wtf/OwnPtr.h"
 #include "wtf/PassOwnPtr.h"
@@ -120,25 +121,32 @@ public:
     PassRefPtr<ShapeResult> shapeResult();
     ~HarfBuzzShaper() { }
 
-private:
-    struct HarfBuzzRun {
-        const SimpleFontData* m_fontData;
+    enum HolesQueueItemAction {
+        HolesQueueNextFont,
+        HolesQueueRange
+    };
+
+    struct HolesQueueItem {
+        HolesQueueItemAction m_action;
         unsigned m_startIndex;
-        size_t m_numCharacters;
-        hb_direction_t m_direction;
-        hb_script_t m_script;
+        unsigned m_numCharacters;
+        HolesQueueItem(HolesQueueItemAction action, unsigned start, unsigned num)
+            : m_action(action)
+            , m_startIndex(start)
+            , m_numCharacters(num) {};
     };
 
+private:
     float nextExpansionPerOpportunity();
     void setExpansion(float);
     void setFontFeatures();
 
-    bool createHarfBuzzRuns();
-    bool createHarfBuzzRunsForSingleCharacter();
-    PassRefPtr<ShapeResult> shapeHarfBuzzRuns();
-    void shapeResult(ShapeResult*, unsigned, const HarfBuzzRun*, hb_buffer_t*);
+    inline bool shapeRange(hb_buffer_t* harfBuzzBuffer, int startIndex, int numCharacters, const SimpleFontData* currentFont, UScriptCode currentRunScript, hb_language_t);

[eae, 2015/10/14 08:12:01]

How about using unsigned for startIndex and numCharacters?

+    bool extractShapeResults(hb_buffer_t* harfBuzzBuffer, ShapeResult*, Deque<HarfBuzzShaper::HolesQueueItem>*, bool& fontCycleQueued, const HolesQueueItem& currentQueueItem, const SimpleFontData* currentFont, UScriptCode currentRunScript, bool isLastResort);
+    bool buildHint(Vector<UChar32>& hint, bool needsList);

[eae, 2015/10/14 08:12:01]

This could use a better name or a comment.

+
+    void insertRunIntoShapeResult(ShapeResult*, PassOwnPtr<ShapeResult::RunInfo> runToInsert, int startGlyph, int numGlyphs, int, hb_buffer_t*);
     float adjustSpacing(ShapeResult::RunInfo*, size_t glyphIndex, unsigned currentCharacterIndex, float& offsetX, float& totalAdvance);
-    void addHarfBuzzRun(unsigned startCharacter, unsigned endCharacter, const SimpleFontData*, UScriptCode);
 
     OwnPtr<UChar[]> m_normalizedBuffer;
     unsigned m_normalizedBufferLength;
@@ -148,9 +156,10 @@ private:
     unsigned m_expansionOpportunityCount;
 
     Vector<hb_feature_t, 4> m_features;
-    Vector<HarfBuzzRun, 16> m_harfBuzzRuns;
+    Deque<HolesQueueItem> m_holesQueue;
 };
 
+
 } // namespace blink
 
 #endif // HarfBuzzShaper_h